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perf(json): avoid first-char regex for direct JSON bodies #744

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perf(json): avoid first-char regex for direct JSON bodies #744

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22 changes: 11 additions & 11 deletions lib/types/json.js
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ const { normalizeOptions } = require('../utils')
module.exports = json

/**
* RegExp to match the first non-space in a string.
* RegExp to match the first non-whitespace character in a string.
*
* Allowed whitespace is defined in RFC 7159:
*
Expand All @@ -33,7 +33,7 @@ module.exports = json
* %x0A / ; Line feed or New line
* %x0D ) ; Carriage return
*/
const FIRST_CHAR_REGEXP = /^[\x20\x09\x0a\x0d]*([^\x20\x09\x0a\x0d])/ // eslint-disable-line no-control-regex
const FIRST_NON_WHITESPACE_REGEXP = /^[\x20\x09\x0a\x0d]*([^\x20\x09\x0a\x0d]|$)/ // eslint-disable-line no-control-regex

@bjohansebas bjohansebas Jul 9, 2026 •
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Okay, for future reviewers, here's the regex change.

" {json}"
master=match[1]="{"
PR=match[1]="{"
"123" (primitivo)
master=match[1]="1"
PR=match[1]="1"
" " (solo whitespace)
master=NULL (no match)
PR=match[1]=""
"" (vacio)
master=NULL (no match)
PR=match[1]=""


const JSON_SYNTAX_CHAR = '#'
const JSON_SYNTAX_REGEXP = /#+/g
Expand Down Expand Up @@ -80,10 +80,12 @@ function createJsonParser (options) {
return {}
}

const first = firstchar(body)
if (first !== '{' && first !== '[') {
debug('strict violation')
throw createStrictSyntaxError(body, first)
if (body[0] !== '{' && body[0] !== '[') {
const first = firstNonWhitespaceChar(body)
if (first !== '{' && first !== '[') {
debug('strict violation')
throw createStrictSyntaxError(body, first)
}
}

try {
Expand Down Expand Up @@ -152,12 +154,10 @@ function createStrictSyntaxError (str, char) {
* @returns {string|undefined}
* @private
*/
function firstchar (str) {
const match = FIRST_CHAR_REGEXP.exec(str)
function firstNonWhitespaceChar (str) {
const match = FIRST_NON_WHITESPACE_REGEXP.exec(str)

return match
? match[1]
: undefined
return match && match[1] ? match[1] : undefined
}

/**
Expand Down